The correct answer is (a) Dara Shikoh.
Dara Shikoh was the eldest son of Mughal emperor Shah Jahan. He was a learned man and a poet. He was also a follower of Sufism. In 1658, he was defeated by his younger brother Aurangzeb in the war of succession. He fled to Srinagar (Garhwal) and took asylum there. He was later captured and executed by Aurangzeb.
(b) Suleiman Shikoh was the second son of Shah Jahan. He was not involved in the war of succession. He died in 1658, a few months before his father.
(c) Mirza Mughal was the third son of Shah Jahan. He was also not involved in the war of succession. He died in 1661.
(d) Nazawat Khan was a Mughal nobleman. He was not involved in the war of succession. He died in 1664.